The environmental control systems, ECS, in current jet-engine powered aircraft, are typically powered by engine bleed-air: that is, air tapped from different stages of the main engine's compressor. Examples of such bleed-air powered ECS for aircraft may be found in U.S. Pat. Nos. 2,777,301 to Kuhn, 2,851,254 to Messinger et al, 3,369,777 to Furlong, and 3,711,044 to Matulich.
In prior art bleed-air systems, the bleed-air serves as a source of hot/pressurized air which is used to power the ECS to accomplish cabin pressurization, cabin heating, cabin-cooling, and cabin-humidity control. Typically, for the ECS, the energy in the bleed air is conditioned by a control system which insures that the cabin pressure is maintained at comfortable atmospheric levels to aircraft altitudes up to 42,000 feet, and that the air supplied to the cabin has acceptable moisture content, temperature, and freshness.
The aforementioned practice of bleeding the engine compressor air has several disadvantages. In extracting this bleed-air, the thermodynamic balance of the engine is adversely affected, with a consequent loss of engine thrust and, even more importantly, with a consequent undesirable fuel-increment penalty. In addition, the engine is typically made mechanically complex by the provisioning of bleed ports at two or more stages of the engine compressor. In the quest for fuel-efficient air-transports, it is essential that the method of extracting power for the ECS be optimized from a power and fuel consumption point of view.
In some special cases, and particularly in the case of earlier piston-engine aircraft, engine-driven compressors were used to power aircraft ECS. These compressors, like the bleed air, serve as a source of hot/pressurized air which is used for the ECS functions enumerated hereinabove. Examples of the use of engine-driven compressors to power aircraft ECS may be found in U.S. Pat. Nos. 2,585,570 to Messinger et al, 2,614,815 to Marchant et al, 2,678,542 to Stanton, and 2,697,917 to Mayer.
While engine-driven compressors eliminate the need for engine bleed for the ECS, they have many inherent disadvantages, including the following, (1) The compressors must be designed to meet the torsional-vibrations and other hostile environments of the engine; (2) The compressors are heavy and demanding of much space/volume; (3) The compressors require mechanical disconnects, to protect the engine drive against mechanical-failures, or seizures of the compressors; (4) Significant ducting must reside in the engine power plant area and must be brought out of the power plant into the aircraft; (5) The transit of the ducting from the power plant, through the pylons, through the wings, etc., impose problems of weight, customized duct-installation, high labor costs, and high material costs; (6) Engine driven compressors do not have viability and flexibility of operation; for example, engine-driven compressors cannot pressurize the airplane without running the engine and cannot be switched off easily, when not required; and (7) Engine-driven compressors require an external air-source, if the (onboard) auxiliary power unit (APU) cannot be run for extended periods of time.
In view of the problems associated with the above prior art approaches, there is a need to develop an efficient, economical, flexible, and energy efficient system for providing power to aircraft ECS.
From the foregoing, it can be seen that it is a primary object of this invention to provide a novel system for providing power for aircraft ECS and thereby eliminate the need for bleeding the engines or using engine-driven compressors. Such a system would then eliminate or lessen to a great extent the several disadvantages discussed hereinabove with relation to the prior art engine bleed and mechanically driven compressor approaches.
A further object of this invention is to provide an "all-electric" ECS for modern advanced transport aircraft (ATA), in which the primary source of energy is derived from one or more electric motor-driven compressors.